Psychometric evaluation of the Glaucoma Symptom Identifier

Area of Science:

• Ophthalmology
• Psychometrics
• Quality of Life Research

Background:

• Glaucoma significantly impacts patients' quality of life, yet it is often perceived as asymptomatic.
• There is a need for validated tools to assess glaucoma symptoms and their effect on daily functioning.
• The Glaucoma Symptom Identifier (GSI) was developed to provide a comprehensive, one-page assessment of glaucoma's impact on quality of life.

Purpose of the Study:

• To evaluate the psychometric properties of the Glaucoma Symptom Identifier (GSI).
• To confirm the GSI's utility in assessing glaucoma symptoms and quality of life in clinical practice.
• To establish the GSI as a tool for both physicians and patients to understand glaucoma's effects.

Main Methods:

• A cross-sectional online survey was conducted with 718 participants aged 40+ with self-reported glaucoma.
• Item response theory (IRT) was employed for psychometric evaluation of the GSI.
• The GSI's scores were compared with the SF-12, a generic quality-of-life instrument.

Main Results:

• The GSI demonstrated good reliability, convergent validity, and discriminant validity.
• The questionnaire effectively captured the impact of glaucoma across a range of disease severities.
• IRT modeling and respondent feedback identified areas for potential questionnaire improvement.

Conclusions:

• The Glaucoma Symptom Identifier (GSI) is a psychometrically sound and valid tool.
• The GSI is suitable for self-administration by glaucoma patients in routine clinical practice.
• The GSI facilitates assessment of current and potential future glaucoma symptoms for both patients and physicians.